Intracellular DNA intermediates of the parvovirus, KRV, are usually found associated with proteins with a capsid-like structure forming nucleocapsids. We have examined the replicative intermediate DNA of KRV to determine the associated characteristics of the protein(s). Protein is found associated with the 5' termini of the KRV double-stranded replicative intermediate. The molecular weight of the protein determined by electrophoresis in acrylamide gels is about 68,000. The protein remains attached to the DNA after centrifugation in alkaline cesium chloride. The stability of the DNA-protein linkage in alkali is believed to be due to a covalent linkage. The terminal amino acid in the DNA-protein linkage was determined to be phosphoserine. The terminal nucleotide is thymidine or cytidine. We hope to further investigate the function of the protein. We also hope to determine by peptide mapping and amino acid sequencing the relationship, if any, to the KRV capsid proteins.